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  home savings

What it's really like to install and own an 8kW residential solar system in Phoenix, AZ.

Here's the section everyone is interested in... the cost savings. I'm including my bills and usage history to compare with my new bills and usage as the information comes in. I am not including the system price as these prices are constantly changing.

Please note that any excess production gets rolled into a usage credit that will be applied toward future use. My power plan has on-peak (expensive) pricing and off-peak (cheap) pricing. On-peak solar production gets applied to on-peak usage, and off-peak production gets applied to off-peak usage. A vast majority of my usage is off-peak, so I don't expect that I'll ever have an off-peak credit. In the winter and spring, I am likely to produce more on-peak electricity than I can use. When the summer comes and my usage increases substantially, my production credit will be applied. My savings for April were pretty small, but the 358kWh of extra production will definitely help in June and July! I expect that the April figures showing a bill of about $90 will be about the lowest that my bills will ever be. This figure includes many base charges and fees that will probably not or cannot be reduced (transmission fees, meter read fees, taxes, etc.).

My home is approximately 3000 square feet, 1 story with 2 air conditioners, built in 1998, with 2x6 construction. An appropriate system size for a home like mine is 6-8kW.

My power company is APS. My plan (Time Advantage 7pm-Noon) defines on-peak as anything used from Noon to 7pm Monday through Friday except major holidays. A kWh of on-peak generation is worth $0.24445. I've multiplied my production credit by this rate to estimate savings that will be applied on summer bills.

You can email me if you have any questions.

 

Pre-Solar Feb 09 - Feb 10 Post-Solar Mar 10 - Jan 11
Month Usage
(kW)
Elec Usage Taxes &
Other
Total Usage
(kW)
Elec Usage from APS Taxes &
Other
Total Savings vs. Prior Year On Peak Credit toward Future Use
(kWh)
Mar 1754 $137.45 $8.44 $145.89 1687 $81.76 $5.38 $87.14 $58.75 358 ($87.51)
Apr 1920 $159.45 $9.88 $169.33 1717 $75.93 $4.99 $80.92 $88.41

480 ($117.34)

May 3012 $301.94 $19.13 $321.07 1701 $75.41 $4.96 $80.37 $241.57 219 ($53.44)
Jun 2866 $326.33 $20.99 $347.32 2637 $132.87 $10.06 $142.94 $183.39 979 ($238.79)
Jul 3859 $367.96 $23.73 $391.69 3515 $201.42 $14.86 $216.28 $175.41 521 ($127.08)*
Aug 3287 $400.67 $25.89 $426.56 2850 $152.14 $11.59 $163.73 $262.83 317 ($77.32)
Sep 3468 $349.62 $22.52 $372.14 1673 $136.12 $10.38 $146.50 $225.64 264 ($64.39)
Oct 2226 $239.35 $15.27 $254.62 2022 $103.31 $7.88 $111.19 $143.43 257 ($62.68)
Nov 2152 $170.65 $10.75 $181.40 1887 $92.76 $7.07 $99.83 $88.64 505 ($123.16)
Dec 2321 $198.53 $12.58 $211.11 1815 $99.82 $7.61 $61.83** $149.28 692 ($168.75)
Jan 2559 $194.94 $12.35 $207.29 TBD $120.48 $9.19 $129.67 $77.62 251 ($61.21)
Feb 2147 $169.65 $10.54 $180.19 2135 $109.87 $7.89 $117.76 $62.43 333 ($81.20)
*On peak credit from partial February generation of 105kWH not shown.
*One inverter stopped working and was non-functional for about 2 weeks so production was reduced.
**APS issued a credit of $45.60 for excess production and zero'd my credits.

Total savings 2010 vs 2009: $1757.30.


Ongoing bill totals (simple, solar fiscal year):
MONTH 2010 2011 2012 2013 2014 2015
MAR $145.89 $87.14 $70.51 $88.30 $90.79 $89.61
APR $169.33 $80.92 $74.28 $94.67 $79.92 $168.65
MAY $321.07 $80.37 $74.37 $114.62 $124.59 $226.76*
JUN $347.32 $142.94 $129.15 $144.58 $161.12 $240.08*
JUL $391.69 $216.28 $166.58 $183.80 $216.62 $264.96*
AUG $426.56 $163.73 $171.07 $205.23 $211.21 $238.70*
SEP $372.14 $146.50 $153.95 $164.54 $174.88 $218.39*
OCT $254.62 $111.19 $101.47 $118.20 $100.66 $149.29*
NOV $181.40 $99.83 $34.93 $114.99 $114.03
DEC $211.11 $61.83 $29.81 $14.48 $101.96
JAN $207.29 $129.67 $137.65 $157.43 $103.00
FEB $180.19 $117.76 $108.02 $120.93 $81.40
TOTAL $3208.61 $1438.16 $1251.79 $1521.74 $1560.18

*Note: Bitcoin Miner drawing ~450W/h installed